The present invention relates to a source of illumination for a light valve using a plurality of light sources.
Light valves are used in projection video apparatus. A beam of light is expanded to uniformly irradiate the input of a light valve, which modulates the light to produce an image. Three light valve arrangements can be used to modulate light of three different colors, such as red, green and blue, to produce a full color image.
An efficient source of illumination is a laser diode. Laser diodes are now available to produce red, green and blue illumination. However, the light level produced by a laser diode is not sufficient to produce an image of satisfactory brightness when a light valve arrangement is used, for example, in a theater. The instant invention advantageously provides a source of illumination for a light valve which has greatly increased brightness.
A source of illumination comprises a parabolic reflector having an axis and a point of focus on said axis. A plurality of light sources are directed substantially parallel to the axis of the parabola so that the light from the plurality of light sources is reflected to the point of focus of the parabolic reflector.
A projection light valve system, in which a source of light illuminates a light valve which modulates the illuminating light to produce an image, comprises a parabolic reflector having an axis and a point of focus. A plurality of sources of substantially monochromatic light are each directed toward the parabolic reflector in a path substantially parallel to the axis of the reflector so that the light reflected from the reflector is directed toward the point of focus of the reflector. Optical means are positioned at the point of focus for forming a beam of light from the light reflected from the reflector. Means are located between the optical means and a light valve device for expanding the beam of light to substantially uniformly illuminate the light valve device.